Telephone-exchange system



May 6, 1930.

s. H. EVERETT TELEPHONE EXCHANGE SYSTEM Filed Jurie 6, 1928 4'Sheets-$het m/VE/vmfi SAMUEL EVERETT Arm/war y 6, 1930. s. H. EVERETT I1,757,708

TELEPHONE EXCHANGE SYSTEM Filed June 6, 1928 Q? Q ii ii 4 Shets-Sheet 2/NVEN7'0/? SAMUEL h. EVERETT y 1930- s. H. EVERETT 1,757,708

TELEPHONE EXCHANGE SYSTEM Filed June 6, 1928 (Sheets-Sheet 3 /N|/EN70/?SAMUEL h! EVERETT ATTORNEY TELEPHONE EX CHANGE. SYSTEM Filed June 1928 4Sheets Sheet 4 IN VENTUR SAMUEL /7f EVERETT BY ATTURNEX eo-aasirenlPatented May 6, 1930 SAMUEL I1. EVERETT, OF TEANEGK, NEW-- JEnsEY,,-ssIeiva To BELL TELEPHONE LABORATORIES, INCQRPORATED, or NEW ,Yoan,.1\i-. Y,; a CORPORATION or NEW Yam: 1

Application filed fiune 6,

trunking systemsand more particularly to The object of the invention isto simplifyv an arrangementfor trunk circuits of this character whichcombines master or 'commonkey ringing with automatic listening.

7 and reduce the amount of ringing apparatus at a straightforwardautomatic listening position, thereby eifecting economies in space andequipment and facilitating the completion of connections. This makes itpossible for an operator to handle a greater number of calls within agiven period.

The principal feature of the invention, therefore,"1s the provision ofmeans for adapting master ringing keys to automatic:

listening trunk circuits.

. Other features will appear from the following description when read inconnection with the accompanying drawings which when placed together,with Fig. 2 at the right and Fig. 3 below Fig. 1, and Fig. 4 below Fig.2

and to therightof Fig. ,3, represent a group of three straightforwardtrunk circuits, to-

gether with common positional eqiupinent, in accordance-with theinventlon. 1 I

It will'be assumed that a calling subscriber I A (Fig. 1) desires to beconnected with a subscriber B. (Fig. 2) and that an A operator at whosepositionthe calling subscribers line terminates has connected thesubscribers line by means of a cord circuit 2 with the first idle trunkcircuit (T extending to the desired distant exchange which isrepresented by thetrunlr equipment shown to the right of the'brokenvertical linev 11 (Figs. 1 and 2) andby the common equip ment shown byFigs; 3 and4. .4

When the A operator inserts the calling end of the cord 2 in the jack 3,line relay 4 operates in an obvious circuit, which iirturn lights theguard and disconnect lamp 5 in.

a" circuit which can be traced from ground, contacts ofrelay 4,conductor 6, contacts 7 of relay 8, contacts 9 of relay 10, resistance11 .and lamp 5 to battery. Relay 4 also operatesrel'ay 12 over 12 inoperating actuates the start relay 13 associated with this'particulartrunk, the cir- Ielays 33an d 34 scr ption.

. TELEPHONE-EXCHANGE SYSTEM 1928. i Serial No. 283,205. r

[ tacts 180 of relay '179to battery. Relay 13 in operating completes acircuit for operating relay 27,iwhich can be traced from bat tery,winding of relay 27, contacts 28 of relay 13, conductor 29, contacts 30of relay 31, conductor: 32, relay 33 and the normal con- "tactsof relay34 to ground,

. Relay. :33 operates'in this circuit, supplies ground; atlllSJQlltiLCtS 35t0 lock itself in the beforeetraced c rcuit and byclosing its contacts 36 completes an energizing circuit for.vslow-releasing relay 34, which in operating removes theoriginaloperating ground for; the circuit first traced.

will appear later in the dei-Relay-27 operates in series with relay 33and isheld operated by ground at contacts 35.of.relay 33. I r y Relay 3in operating opens at its contacts the energizing circuit for .relayscorrespondingto 27 associated with all the trunks having a number higherthan T as, for exta v Relay 2'? in operating opens at its contacts 38the energizing circuit for relays corresponding to relay 13 associatedwith all trunks having a lower number than for. example, T r 7 Relay 27in operating also closes its contacts 39, thereby completing a circuitfor relay 40 (Fig. ,4), which can be traced from battery through thepilot lamp 41, contacts 39 ofrelay-27, conductor 42, contacts 43 of thatwhen-theoperator has her telephone set wOT (Fig. 3) plugged into jacks45 and 46, an ob 'vious circuit including conductor 6. Relay relays 47,48, 49fand 44 operate insequence and remain operated as long as theoperator occupies the position. V

4. ,When' r.e1ay:27 operated it also closed its The function of cuit forwhich can be traced from ground,

' contacts 53 which, together with the'closure- 7 of contacts 54 ofrelay 40, completes a circuit for flashing the guardanddisconnect lamp 5by periodically short-circuiting it under control of interrupter 55.This short-circuit canbe traced from the upper terminal of the lamp 5,contacts 53 of relay 27, conductor 56 and contacts 54 of relay 40* tothe interrupter 55, which in operating periodically connects battery tothe upper terminal of lamp 5, which in effect short-circuits andmomentarily extinguishes it. 7 r

The operation of relay 27 further performs the function of operatingrelay 57 which connects the'trunk T into the position circuit andultimately causes the operators telephone set OT to be. connected to thetrunk.

The circuit for operating relay 57 can be traced from battery, contacts58 of relay 12,

conductor 59, contacts 60 of relay 20, upper winding of relay 57,conductor 61, contacts 62 of relay 27, contacts 63'of relay 13,conductor 64, contacts 65 of relay49, conductor 66, resistance 67,contacts 68 of relay-69 and'contacts 70 of relay 71 to ground. 1

Relay 57 in operating, as before stated, connects the trunk into theposition circuit and at its contacts 72, 73 and 74 connects the trunkrelays 18 and 75 over conductors 76,

77 and 78, respectively,-to the common ringing key equipment shown atthe bottom of Fig. 4.

Relay 57 also operates; relays 79 and 80.

I The circuit for relay 79 can be traced from battery, contacts 81 ofrelaylO, lower winding of marginal relay 20, contacts 72 of relay 57,conductors 76 and 82, contacts 83of relay 49, conductor 84,'and windingof relay 79 to ground. Due to the resistance of relay 79,

relay 20, which is marginal, does not operate at this time. Theoperation of relay 79 performs no function at this time other thanprepare a circuit for operating certain relays when any one of themaster ringing keys M,

J, R, V or TK is depressed to be hereinafter described.

The'operating circuitfor relay80 can be I traced from ground, contacts86 of relay 87,

winding of relay 80, conductor 88, contacts 89 of relay 48, conductor:90, contacts'91 of relay 57, upper winding of relay 57, contacts 60 ofrelay 20, conductor59 and contacts 58 of relay 12to battery. This lasttraced circuit, which was completed at contacts91 of undercontrol ofmarginal relay 20, which relay57, serves tohold relay 57 operated willnot operate until a ringing key is depressed.

Relay in operating completes an obvious circuit for operating relay 71,which in attracting its armature removes ground from conductors 66 and64. In cases whenthe operator has reconnected her set to the trunk bymeans of thelistening key 99, this removal ot ground prevents any othertrunk relays,

corresponding to relay 57, from operating until the operator hasfinished with. the pres-.

ent trunk and is released therefrom.

When relay 71 operated it closed, at its contacts 100, a momentarylocking circuit for itself under control of relay101, which lockingcircuit canbe traced from battery, winding of relay 71, conductor 102,contacts 103' of relay 104, contacts 105 of relay 101, con- I tacts 106of relay 44, conductor 107 and contacts 100 of relay 71 to ground.

By openingits contacts 92, relay 71 re moves battery from the circuitextending through contacts 93 of relay 94, winding of relay 95,conductor 96,- contacts 97of relay 49, and conductor 98 to the emergencylistening keys'such as99, one of which is asso: ciated with each of thetrunksT, T T etc.,

thereby preventingthe operation of any other relay corresponding torelay 57 in case the listening key of another trunk should be actuatedbefore the operator is released from the present trunk.

Relay 71 in operating alsocloses a circuit to energize relay 108, whichcan be traced from battery, contacts 109 of relay 71, conductor 110,contacts 111 of relay 44, contacts 112 of rela 104 and winding of relay108 to ground. elay 108 in operating causes the consecutive operation ofrelays 113, 114, 115, and 101, the operating circuits of which areobvious. V

WVhen relay 108 operates it closes its contacts 116 and 117, whichconnect the secondary or left hand winding of transformer 118' to thetrunk over contacts'119 and 120 of relay 101, contacts 121 and 122 ofrelay 48, conductors 123 and 124, and contacts 125 and 126 of relay 57.Relay 108 also closes, at its contacts 127, a circuit for interruptedbattery through the primary orlright hand winding oftransformer 118 toground, thereby cans closes, as its-contacts 129, a new and obviouscircuit to ground for the interrupted battery associated withtransformer 118,-which thereupon generates a' second a. c.impulsewhi'chis transmitted-to the trunk. Relay 114 also closes, at its innercontacts, a circuit to energize relay 115. which opens'its contacts 130and disconnects ground from the transformer primary, thereby cutting offthe induced current a second time.

The connection and disconnection of alternating current of audiblefrequency to the V au ' 49, conductor 139 and contacts trunlntwicerepeated by the consecutive operation of relays 108, 113, 114 and 115,gives the effect of two short zips of :tone flowing backover the trunkto the calling exchange as a signal to the calling opera-tor to pass thenumber of the desired subscriber.

Relay 115 also closes its outer left contacts thereby completing anobvious energizing circuit for relay 101 which operates and disconnects,at its contacts 119 and 120, the

transformer 118 from the trunk and substitutes the .operators' set OT byclosing its con tacts 131 and 132, whereupon the calling operator andthe incoming trunkoperator are in direct telephonic communication.

After the trunk operator has received the number and party designation,if any, of the called subscriber, she proceeds to setup the connectsground to cause the operation of relay 134 in a circuit which includesthe winding of relay 85 and contacts of'operated relay 79 to battery.Relay 85 operates in series 'with relay 134 and both relays are. lockedup in the following circuit: Battery, upper contacts and winding ofrelay 85,

winding and contacts 135and. 136 of relay 134, conductor 137, contacts138 of relay 140 of relay 71 to ground. 7

When relay 134 operated it closed its con tacts 136 and 141,'therebyconnecting ground,

supplied over conductor 137 from relay 71,

to conductors 77 and78, which causes the operation of relays 18 and 75in-the trunk circuit. Relay 18 looks up over itscontacts 148, contacts15 of relay 16, and contacts 14 of relay 12 to ground, and relay 7 5.looks up at its contacts 149 over the same circuit. Re-

lays 18 and 75 are therefore held up under control of the tripping relay16.

Relay 134 also closes its contacts 142, which connects ground, suppliedover conductor 137 to operate relay 143, which relayin operating closesits contacts 144, and connects ground,

tacts 15 of relay 16 and contacts 14 of irelay 12 to ground.

Both relays 18-and 20 open the circuit re- I viously tracedforenergizing relay 13 which now releases and in turn releases relay 27.

Relay 27 thereupon opens its contacts 39 which deenergizesj relay 40,thereby removing'the flashing condition from lamp 5 and I permitting itto burn steadily.

Relay20, by opening its contacts 60,"causes relay 57 to release, whichopens it's-multiple connects the trunk from the position equipmentincluding the operating telephone,as

shown in Figs. 3 and'4. Relay 20 also causes the release of relays 80,71, 9 4, 69, 108,113, 114, 115 and'lOl.

a 0 contacts 125, 7 3, 91, 72, 74 and 126 and d1s The trunk operator nowmakes the usual busy test by touching the tip of plug 149 to the sleeveof jack 133 and, if she hears no clic lninserts-the plug into the jack,whereupon sleeve. relay 8 operates in an obvious circuit. Relay 8disconnectsthe busy test conductor 150 from the trunk and connects thetip of the trunk plug through contacts of relay 151 to the upper half ofthe right hand winding of repeating coil 152. Relay 8 also :opens itscontacts'7, thereby extinguishes the guard and disconnect lamp 5,

and byclosing its contacts 153, prepares-a1 circuit for operatingringing relay 151, which is energized when the pick-up interrupter" 154connects battery to conductor 155. p

, The circuit for relay 151 can be traced from ground, contacts 153 ofrelay 8,'conductor 156, contacts 157 of relay 2 0, winding of relay.151, contacts 158 of the same relay, contacts 159 of relay '18, andconductors to battery when the commutator of interrupter 154 is in theproper position. v Relay 151 looks up, at its contacts 160, overconductor 59 and contacts 58 of relay 12.to battery. 6 Positivepulsating ringing current is now connected to the tip-side of the calledline at contacts 161* ofrelay 151 and ground is connected to thering-side at contacts 162,

which causes the polarized armature of the r M party ringer on thecalled line tovibrate.

/Vhen the calledsubscribe-rs receiver is removed from the switchhooktripping relay 16 operates inthe usual manner due to increased currentflowing through its winding.

Relay 16 releases relays .20, 75 and 18 and the release of relay 20opens theho-lding circuit of relay 151, which releases and disconnectsringingz cur'rent from the called line.

When relay 151 releasesit retracts its ar maturesandshort-circuits.condensers163 and 164, thereby completing a circuit forsupplying battery to the called line and operating supervisory relay165. Relay 165 causes reversing relay. 166 to operate, which reversesthe current flow in the calling end of the trunk, thereby givingsupervision to the A operator at the originating ofiice in theusualtoagainreverse the current-flow ,inthe trunk,

thereby giving the A 7 operatorat' the originating oflice the usualsignal that the called subscriber has hung up;

. When the originating operator dlsconnccts cord circuit 2 from thetrunk jack 3, relay 4 releases, which in turn=releases relay 12. Belay.12 released, closes an energizing circuit for relay 10, which can betraced from batter lower back contacts of relay 12,

5 as a disconnectsignal.

windingof relay 10 and contacts 153 of relay 8 to ground. Relay 1Ooperatedlights lamp be traced from gronnd, contacts 153 of relay 8,contacts167 of relay 10, resistance 11 and lamp 5 to-battery. RelaylOalso locks up in the following circuitz Battery, contacts 168,-winding'of relay 10, and contacts 153 of relay 8 to ground.

. lVhen the trunk operator withdraws plug 149, relay 8 releases whichreleases relay 10. Relay 10 in turn extinguishes lamp 5 and restores thecircuit to normal.

In case the trunk operator isrequested to ring J instead of M sheoperates ringing the'lamp 5, thus permitting it to burn steadily. y

Relay .169 also operates relay 143 which in turn operates relay 20 whichopens the looking circuit previously traced for relay 57 which nowreleases and disconnects the trunk from the common equipment shown inFigs. 3 and 4. Relay 20 in operating also causes relays 80,71, 94, 69,108,113, 114., 115, and 101 ously described.

to release. L

lVit-h relay 18 only-operated negative pul-.

sating current is connected to the tip of the called line and relay-151-operates as previ- In caseparty R is desired key R is de pressed, whichcauses the operation of relay 170,- which in turn operates relays 75 anda 143. The effect of the operation o1 relay 143 is the same aspreviously described.

Relay 75,- being operated alone, connects positive pulsating current tothe ring side of the called line when relay 151 operates as previouslydescribed.

If the 1V party is desired the operation 6 of key 1V causesthe operationof relays 171 and 143 in sequence. X Relay 171 has no efiect on eitherrelay 18 or and therefore relay '151, when operated,is effective tovconnect negative pulsating current to the ring side and ground to thetip of the calledline.

Ifinstead of being connected to a subscribers line the trunk T is to befurther extended over another trunk circuit, not

shown, ringing on the outgoing trunk should be prevented and, therefore,for this purpose a fifth key, designated TK, is provided This circuitcan which when operated causes the operation of relay 146. Relay146operates relay 18, which releases relays'13, 27- and 40. The release1 When the operator plugs into the outgoing trunk the sleeve relay 8will operate as usual,

thereby extinguishing the lamp 5. However,

ringing relay 151 cannot operate as before; for the reason that itscircuit is open at contacts 157 of relay 20, this relay having beenprevented from operating by the opening of contacts 145 whenrelay 146operatedl in response to the actuation of the trunk or non-ring key TK.-Ringing is, therefore, prevented under the foregoing condition by thenon-operation of relay 151.

It may happen that the trunk operator receives an order to extend thecalling trunk to a line which is markedin such a manner as to indicate,for example, that the line is out of order, the number has been changed,

. or service is denied, etc., and under this condition the switchingoperator is instructed to plug the calling trunk into what is known asan intercepting trunk leading to a special operator who inquires thenumber being called and endeavors to either arrange' for completion ofthe callv or to explain to the calling subscriber why the call cannot becompleted. r v

'If, for example, the called subscribers number has been. changed, thespecial operator will ascertain the present number and pass it to theswitching operator over a loopback circuit, not shown, whereupon theswitching operator will disconnect from the intercepting trunk and makeconnection with the called subscribers new number.

When the switching operator pluggedinto the intercepting trunk, sheoperated the nonring key TK, thereby operating relay 18 in the callingtrunk circuit which at once looked itself to relay 12'under control ofrelay, 16.

Due to the'fact that the operating circuit forv relay 151 is open atcontacts 157 of relay 20, which relayis not operated under the no-ringcondition, relay 151 is not energized to connect ringing current to theline and, therefore, tripping relay 16 is not operated when the calledoperator answers. Under this condition relay 18 would remain locked upuntil the A operator disconnects, except for the provision of some otherrelease means, which will now be described.

The release of relay 18 after disconnection of the calling trunkYfronian intercepting trunk is accomplished in the following man-. ner: Afterthe intercepting operator informs pared for the operation of relay 57"inthe trunk circuit and relay 95 in the common ringing key circuit(Fig. 4). This. circuit can be tracedfrom ground at line relay 4,

conductor 6, contacts 7 of relay 8, contacts 9 of relay 10, conductor174, lower winding of relay 57, contacts of key 99, conductor 98,contacts 87 of relay 49, conductor 96, winding of relay 95, contacts 93of relay 94, and contacts 92 of relay 71 tobattery. Relay 57 operates toconnect thecommon equipment to the trunk once more and locks in thefollowing circuit Battery, contacts 58 of relay l2, conductor .59,contacts 60 of relay 20, upper winding andcontacts 91 of relay 57conductor 90, contacts 89 of rela-y48,con-

ductor 88, winding of relay 80, and contacts r and the originating or A?operator has dis- 86 of relay 87 to ground. 7

Relay 80 is effective through the operation of relay 71 to start thetone relays 108, etc., in operation and to cause the ultimate connectionof the operators telephone OT tov the trunk as previously described. r

Relay 95 (Fig. 4) which operated in series with relay 57 'when key 99,was depressed, operates relay 181. Relay 181locksitselfop erated overcontacts 182 to ground at contacts 140 of relay 71 which operated inresponse to the operation ofrelay 80. V

Relay 181 also closes its contacts 183 thereby short-circuiting relay18in the trunk circuit and causing it to release. This circuit canbetraced from battery, contacts 183 of relay 181, contacts 184 of relay85, conductor 7 7 contacts 73 of relay 57, to one terminal of thewinding of relay 18 the other terminal of which is also connected. tobattery.

The circuit is now in readiness for a new setting of the commonringingkey circuit.

If however the operator had already operated one of the ringing keys M,J, R, orW and plugged into the intercepting trunk, either relay 18 wouldnot be operated in the case of R- orWV, or would operate when key M or Jwas'operated; In this case the intercepting trunk is so arranged thatthe ringing will be automatically trippedwhen the intercepting operatoranswers thereby causing thecircuit to function in the usual manner-andrelease-relay18 ifoperated.

It should be noted that pilot lamp '41, under normal conditions, issteadily lighted inresponseto connection ofthe operators set to acalling trunk in conjunction with the flashing of the guard anddisconnectrlamp 5. However,"1n the case of lnterceptlng service when theoperator has reconnected herself to aftrunln'by operating key. 99, relay181 is operated which in turn operates relay 52 to hold open theenergizing circuit for flashing relay, 4 which circuit alsoincludes thepilot lamp 41., This prevents" pilotrlamp 41 from being. lighted whenthe operator reconnects to the trunk as the light-ing of this lamp,under theseconditions, would give a misleading indication to asupervising operator of the manner in which the operator was hair dlingcalls at her position.

If the trunkoperator plugs into the jack of the called line beforepressing a ringing or the non-ring key, lamp 5 will continue to flash asan indication to the operator that she has .not set the ringingcombination. l/Vheni a ringing or non-ring key is'operated the lamp 5is'extniguished and the oper ator,s telephone and common ringing keyequlpment, as shown 1n Figs. '3 and 4, are disconnected from the trunkby the release of relay57 which isbrought aboutby theoperationof relay20 or relay. 87, depending upon whether a ringing or non-ring key isoperated.

' If after the called subscriber has hung up connectedithe cord 2 fromthe trunk, and before the'trunk operator. has removed the plug 149 fromthe called line, the A or originating operator reselects the trunk T byI againconnectingthe cord 2 with the jack 3,

13, conductor '24, contacts 25*of relay 26 to battery. I 1

In casethe operator should, through force of habit, operate one offtheringing keys' after receiving the new order andbefore disconnecting thetriink from It-he previously called line, such action will beineffective to set the ringing and release relays 13, 27, etc, for thereason that the operating circuit for relayi 79 is held open at contacts81 of'relay 10; With'rela-y 79 normal, the operating path for. relays134, 169 170, 171-an d 146 isopen and nothing happens until the plug 149is freed from the jack, whereupon relay 8 is released, followed by relay10, which in turn operates relay 79 which prepares a circuit for theproper functioning of the master ringing key equipment. 7 f o The lamp 5which started flashing as soon as relay 2'? operated, continues to flashafter plug149 is removed from ack 133, and unti v aringing key isoperated. f

desired to reestablish immediate connections with a trunk Which haspreviousy been released, the operator may operate emergency trunklistening key 99 which completes an auxiliary operating circuit forrelay 57'which can be "traced from ground, contacts of relay l,conductor 6, contacts 7 of relay'8, uppermost contacts of relay 10,conductor 174C, lower winding of relay 57, contacts of key 99, conductor98, contacts 97 of relay 49, conductor 96, winding of relay 95, contacts93 of relay94l and contacts 92 ofrelay'71 to battery. The operation ofrelay'57 will connect the operators telephone and the common ringingequipment to the trunk in the same manner as before described inconnection with automatic listening except that lamp 5, if lighted byreason of a waiting call, will not flash due to the fact that relay 27is not operated. lVhen relay 57 operates it locks up in the beforedescribed circuit, which includes relay 80, Relay 80 operates and closesa circuit to operate relay 71, which last relay disconnects, at itscontacts 92, the battery previously supplied over conductor 98 to allthe listening keys-such-as 99. This prevents two trunks from beingsimultaneously connected to the common listening circuit by actact 112,the emergencycircuit for the" first of the tone relays 108 and, at itscontact 103,

opens conductor 102 thereby preventing relay 71 from locking up when itis operated in response to the operation of atrunk listening keysuch as99.

Relay 104 also connects, at its contacts 176 and 177 the operatorstelephone set to the armature side of contacts 125 and 126 of relay 57over contacts 121 and 122 of relay 4-8 and conductors 123 and 12 1. Whenrelay 57 is operated by the actuation of key 99, the operators set isconnected to the trunk.

In addition to the foregoingfunctions relay 104.- closes contacts 178thereby energizing relay 17 9, ground for which can be traced from theinner contacts of relay 47.

Relay 179 disconnects battery from lead 180 thereby preventing anyof thetrunk sequence relays 13, 31,-etc., from operating in response'to a callover its assor ziated trunk circult. I I 1 i i What IS claimed is 1.In'atelephone system, aplurality of lines, a ringing key equipment and anoperators telephone set common to said lines, and means responsive tothe initiation of a call over one of saicl lines for automaticallyassociating the-ringingjkey equipment. and the operators telephone setwith said line.

2. In a telephone system, an operators position, a plurality of incominglines thereat, a called line, a ringing key equipment and an operatorstelephone set common to said incominglines, means responsive to theinitiation of a call over one of said incoming lines for automaticallyassociating the ringing key equipment and the operators telephone setwith said line, means for connecting said callingline with said calledline, means in said calling line responsive to the actuation of theringing key equipment for the transmission of a ringing signal tothe-called line when said calling line is connected to said calledllne,and means for automatically disconnecting the ringing key equipment andthe claim 1 characterized by meansfortransmit- I ting a signalcomprising a plurality of im pulses of audible frequencyalternating-current over said calling line during the operationsincident to'the connectionof said oper ators telephone to said line.

4. Inna telephone system, an operators position, a plurality of incominglines thereat, a called line, equipment including an opera.- torstelephone set common to said incoming lines, means responsive totheinitiation of a call over one of saidincoming lines for automatically associating said equipment therewith, means for connecting saidcalling line 7 with said called'line, means in said calling line fortransmitting a ringing signal to the called line and switching means insaid common equipment effective to disable said ringing means and todisconnect said commo equipment from said calling line. 5. A system, inaccordance with claim 1 character'izedby a signal device actuated in onemanner in-response to the initiation of said call and in another mannerresponsive to the association of said key equipment and telephone setwith said line, and means responsive to the actuation of said keyequipment for again changing the actuation manner of said signal device.1 j

6. A system, in accordance with claim. 1

characterized by a signal device operating necting said equipment andtelephone set from the trunk to which it is connected.

In Witness whereof, I hereunto subscribe my name this 4th day of June,1928.

' i SAMUEL HJEVERETT.

connecting said ringing key equipment andv telephone set to any one ofsaid lines at will.

8. In a telephone exchange system, an operators position, an operatorstelephone and a ringing key equipment associated therewith, a group oftrunk circuits incoming to said position, means at said position forcontrolling the automatic connection of said operators telephone andringing key equipment to said trunks in a predeterminedsequential orderwhen a plurahty of calls are concurrently extended to said position oversaid trunk circults and means for automatically dlsconnecting thetelephone set and the key equipment from any of said trunks responsiveto the actuation of said ringing key equipment.

9. A system, in accordancewith claim 8 comprising a called line andmeans for connecting a calling one of said trunk circuits to said calledline, characterized by means responsive to a recall on said callingtrunk after the called subscriber has hung up, but before the trunk hasbeen disconnected from the called line, for automatically connecting thetelephone set and ringing key equipment to said trunk in its normalsequence with respect to waiting calls on other trunks of the group.

10. A system, in accordance Withclaim 9 characterized by means forthereafter preventing release of said telephone set and ringing keyequipment from said reselected trunk until said trunk has beendisconnected from the first called line.

11. A system, in accordance with claim 4 characterized by operatorcontrolled means for removing said disabling condition from said ringingmeans after disconnection of said calling line from said called line andbefore the outgoing end of the calling line is released.

12. In a telephone exchange system, the

combination of an A and a B operators position, a plurality of trunkstherebetween, an operators telephone, and a common ringing key equipmentat said. 13 position, means at said B position for automaticallyconnecting said telephone and ringing key equipment to one of saidtrunks when it is seized at the A position, other means at said Bposition operative if a plurality of said trunks are concurrently seizedfor automatically controlling the connection of said operators telephoneto said seized trunksin a predetermined sequential order, and meanscontrolled by said ringing key equipmentfor discon-

